1. Field of the Invention
The present invention relates to a shock absorber for an automobile, more particularly to a shock absorber for an automobile which is designed to exhibit a vibration damping effect in a wide range of a frequency, while suppressing generation of frictional noise.
2. Description of the Related Art
A suspension spring of an automobile, especially, a coil spring is liable to generate resonance with other parts, since natural vibration determined by a configuration frequently appears in integer multiples of a fundamental frequency. Further, the coil spring has a problem of generating large frictional noise between spring seats and the coil spring. Thus, if materials which have a low friction coefficient and excellent vibration damping characteristics throughout a wide range of a frequency are arranged between the coil spring and the spring seats, the above-described inconveniences can be solved at the same time. Therefore, it has been desired to develop the above-described material.
An object of the present invention is to provide a shock absorber for an automobile which can exhibit a vibration damping effect in a wide range of a frequency, while suppressing generation of frictional noise.
In order to achieve the above described object, the shock absorber for the automobile according to the present invention includes a buffer member interposed between parts. The buffer member has a laminated structure including a plurality of vibration damping layers each having a peak of loss tangent tanxcex4 in a range of a frequency which is different from others and surface layers made of thermoplastic resin.
Since a plurality of vibration damping layers having damping characteristics in a range of a frequency which is different from others are stacked as mentioned above, the vibration damping effect can be exhibited in a wide range of a frequency. Further, since the surface layers are made of the thermoplastic resin having a small friction coefficient, noise due to friction can be reduced.
In the present invention, each layer of the vibration damping layers can be made of either of a rubber composition and a composite material including a rubber composition and a thermoplastic resin. The peaks of loss tangent tanxcex4 can be set to various ranges of frequencies different from one another depending on materials of the vibration damping layers.
The present invention is especially preferably applied to the shock absorber for the automobile having buffer members interposed between the coil spring and the spring seats. Since the natural vibration determined by a configuration frequently appears in integer multiples of a fundamental frequency in the coil spring, a plurality of the vibration damping layers, each of which has a peak of loss tangent tanxcex4 in a range of a frequency corresponding to integer multiples of the fundamental frequency, are selected and these plural vibration damping layers are stacked so that the resonance between the coil spring and other parts can be effectively prevented.